Step stool



FIG. 1 is a perspective rear view of the design of the present invention.

FIG. 2 is a rear view of the design shown in FIG. 1.

FIG. 3 is a right side view of the design shown in FIG. 1.

FIG. 4 is a front view of the design shown in FIG. 1.

FIG. 5 is a top view of the design shown in FIG. 1; and,

FIG. 6 is a bottom view of the design shown in FIG. 1.

The broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for the step stool, as shown and described. 